Preparation of Low‐Viscosity Starch Phosphate via Low‐Temperature Dry Process Enhanced by Synergistic Local Electric Field and Far‐Infrared Radiation

ABSTRACT The dry‐process preparation of low‐viscosity starch phosphates remains challenging due to poor mass/heat transfer, low reaction efficiency, and a trade‐off between temperature and by‐product formation. In this study, a low‐temperature dry process enhanced by synergistic local electric field and far‐infrared radiation (LEF–FIR) was employed to produce low‐viscosity corn starch phosphate (CSP) with uniform substitution, using phosphoric acid as the phosphorylating reagent in a spontaneously polarized ceramic (SPC) reactor. The improvements in reaction efficiency, physicochemical properties, and formation mechanisms were investigated to demonstrate that SPC‐CSP achieved the characteristics of low viscosity (65 cp) and minimal by‐product formation, along with favorable physicochemical properties. The esterification mechanism via SPC‐induced LEF–FIR for low‐temperature phosphorylation of starch was elucidated: FIR enabled uniform heating through direct molecular excitation, providing stable thermal conditions; LEF disrupted the structure of starch granules and diminished hydrogen bonding of H 2 O to small water clusters, thereby facilitating the penetration of reagents. This synergistic effect activated reactive sites along molecular chains and promoted uniform phosphate distribution at the C‐2, C‐3, and C‐6 sites, effectively resolving the inherent trade‐off between reaction rate and product quality. This study demonstrates great promise for achieving low‐viscosity starch phosphates with uniform substituent distribution under low‐temperature conditions.